Periodic
trends
The table is a graph in disguise. Plot any measured property against atomic number and the periods appear on their own — that repetition is the whole point of the word periodic.
Property
Connect points by
The rule
→Across a period, increases left to right.
↓Down a group, decreases down a group.
Nuclear charge climbs across a period while the electrons stay in the same shell, so the pull on shared electrons tightens. Down a group the valence shell is further out and screened by more inner electrons, so the pull weakens.
Electronegativity
Pauling
Alkali metalAlkaline earth metalTransition metalPost-transition metalMetalloidReactive nonmetalHalogenNoble gasLanthanideActinide
Highest
- 1FFluorine3.98
- 2OOxygen3.44
- 3ClChlorine3.16
- 4NNitrogen3.04
- 5KrKrypton3.00
Lowest
- 1CsCesium0.79
- 2FrFrancium0.79
- 3KPotassium0.82
- 4RbRubidium0.82
- 5BaBarium0.89
Coverage
Measured100 / 118
18 elements have no published value — mostly the superheavy synthetics, which exist for milliseconds at a time.